One of the most promising courses for further technological development in chemical, pharmaceutical, cosmetic, refining, food products, and many other areas relates to the production of emulsions and dispersions having the smallest possible particle sizes and maximum size uniformity. Moreover, during the creation of new products and formulations, the challenge often involves the production of two, three, or more complex components in disperse systems containing particle sizes at the submicron level. Given the ever-increasing requirements placed on the quality of dispersion, traditional methods of dispersion that have been used for decades in technological processes have reached their limits. Attempts to overcome these limits by mere manipulation of these traditional technologies are often not effective.
Hydrodynamic cavitation is widely known as a method used to obtain free disperse systems, particularly lyosols, diluted suspensions, and emulsions. Such free disperse systems are fluidic systems wherein dispersed phase particles have no contacts, participate in random beat motion, and freely move by gravity. Such dispersion and emulsification effects are accomplished within the fluid flow due to cavitation effects produced by a change in geometry of the fluid flow.
The boiling point of a liquid is defined as the temperature at which the vapor pressure of the liquid is equal to the pressure of the atmosphere on the liquid. For pure compounds, the normal boiling point is defined as the boiling point at one standard atmosphere of pressure on the liquid. If the pressure on the liquid is reduced from one standard atmosphere, the boiling point observed for the compound is likewise reduced from that estimated for the pure compound.
Hydrodynamic cavitation is the formation of cavities and cavitation bubbles filled with a vapor-gas mixture inside the fluid flow or at the boundary of the baffle body resulting from a local pressure drop on the fluid. If during the process of movement of the fluid, the pressure decreases to a magnitude under which the fluid reaches its boiling point for the given temperature, then a great number of vapor-filled cavities and bubbles are formed. Insofar as the vapor-filled bubbles and cavities move together with the fluid flow, these bubbles and cavities may move into an elevated pressure zone. When these bubbles and cavities enter a zone having increased pressure, vapor condensation takes place within the cavities and bubbles, causing the cavities and bubbles to collapse almost instantaneously, which creates very large pressure impulses. The magnitude of the pressure impulses within the collapsing cavities and bubbles may reach 150,000 psi. The result of these high-pressure implosions is the formation of shock waves that emanate from the point of each collapsed bubble. Such high-impact loads result in the breakup of any medium found near the collapsing bubbles.
A dispersion process takes place when, during cavitation, the collapse of a cavitation bubble near the boundary of the phase separation of a solid particle suspended in a liquid results in the breakup of the suspension particle. An emulsification and homogenization process takes place when, during cavitation, the collapse of a cavitation bubble near the boundary of the phase separation of a liquid suspended or mixed with another liquid results in the breakup of drops of the disperse phase. Thus, the use of kinetic energy from collapsing cavitation bubbles and cavities, produced by hydrodynamic means, can be used for various mixing, emulsifying, homogenizing, and dispersing processes.